Marguerite Bouniol, Sophie’s mother and her friend Marie Paul Bloc Daudet pause at the memorial cross that marks the spot where Sophie was murdered outside her holiday home at Toormore, West Cork. Photograph: Niall Duffy

Sophie’s parents, Georges and Marguerite Bouniol, at a memorial mass for her in Goleen, West Cork. Photograph: Provision

Sophie’s parents after placing a bouqet of flowers by a celtic cross marking the spot wher their daughter was found murdered. Photograph: Provision

Sophie’s son, Pierre-Louis

Marguerite Bouniol, at her home in Paris. Photograph: Des Harris/The Picture Desk

Marguerite Bouniol at her home in Paris. Photograph: Des Harris/The Picture Desk

They would give anything to forget, to wipe it from their memories. When Georges and Marguerite Bouniol travelled to Cork to collect the body of their murdered daughter, Sophie Toscan du Plantier, at Christmas 1996, their son Bertrand told them not to look at her.

“I said, ‘We have to say goodbye to our daughter,’” Marguerite recalls. “Her face was crushed to a pulp. They’d tried to fashion a sort of mask with make-up, but it didn’t look like Sophie. They had to cut her beautiful long hair, because it was matted and tangled with blood. I said, ‘That’s not my daughter.’ I couldn’t kiss her. I couldn’t even hold her hand. I try not to remember, so I put photographs of her everywhere, to chase away that dreadful image.”

Sophie is ever present in the graceful, comfortable apartment where she grew up in Paris’s second arrondissement. An oil portrait of Marguerite’s grandmother hangs over the fireplace, above a sepia photograph of Sophie’s great-aunt Alice, who married a marquis. Everyone said Sophie looked like Alice, and she always hung a picture of the marquise in her bedroom.

Sophie’s oriental shawl is spread over the divan, worn thin with the years. Sophie’s favourite painting, a large abstract in pastel colours, hangs on the living room wall. “Here, I find Sophie as she was in life,” Marguerite says.

Seventeen years have passed in a blur of false hopes and disappointments. Georges (87), a retired dentist, and Marguerite, also in her 80s and a former deputy mayor of the arrondissement, seem to shrink before one’s eyes, their dignity and courage no match for the ravages of age and grief.

They heard it on the evening television news. A Frenchwoman on a visit to Ireland had been found dead in west Cork, the presenter said. “It’s Sophie,” Marguerite gasped. Sophie’s telephone didn’t answer. The housekeeper’s number was permanently engaged. A few hours later, the French foreign minister confirmed the awful news. In Cork, their hotel was filled with Christmas decorations and music.

Georges brings Marguerite a glass of water with her Parkinson’s medication. His manner is tender, though Marguerite says suffering has not brought them closer. “I can’t stop talking about Sophie. Georges has absorbed it in silence, so I don’t understand what he’s gone through. I’ve been selfish in my grief.”

Shortly after Sophie was murdered, Marguerite began wearing her daughter’s clothes. “It shocked the family,” she recalls. “It made me feel I was with her, as if she wasn’t gone.”

It was different for the men in the family. “I gave a photograph to her brother Stéphane in New York. He put it away. I asked his wife if they ever talk about it. She said she brought it up once and Stéphane was sick; he lost his lunch.”

Georges sits slumped in the far corner of the dining room, wiping tears from his eyes. Slowly, he enters the conversation. “We’re somewhere else. In the fog,” he says. “This couldn’t possibly have happened to us. We’re not alive. One cannot accept such things. It is a nightmare that never ends. We’ve been in a black hole for 17 years. It’s even worse now, because we realise the guilty person will not be punished. Every time the legal case seems to move forward, it falls apart.”

No one slept in Sophie’s house for a year after she was murdered. “I went alone the second year,” Georges says. “It was hard for me, but I wanted to show we weren’t afraid of the person who killed her. I had the impression we’d left her house to him, and I didn’t want that.”

The December 2003 libel trial, in which Ian Bailey, an Englishman who lives near Sophie’s house, sued eight newspapers for defamation, was a revelation for the Bouniols. Judge Patrick Moran ruled that all eight newspapers had been justified in calling Bailey the chief suspect in Toscan du Plantier’s murder.

“It drives me crazy to read in every newspaper article that Bailey ‘has always denied any involvement’ in Sophie’s death,” Marguerite says. “It’s not true.” At least six witnesses testified or were quoted at the libel trial as saying that Bailey confessed to them. “I bashed her f**king brains in,” Bailey told Malachi Reed, who’d been a 14-year-old schoolboy when Bailey gave him a lift. The other witnesses were Helen Callanan, Yvonne Ungerer, Richard and Rosie Shelley and Bill Fuller.

The Bouniols also learned that Bailey had assaulted his partner Jules Thomas three times between 1993 and 2001, resulting in a barring order. In August 1993, he wrote in his diary, “I actually tried to kill her.” In May 1996, he wrote: “I severely damaged you and made you feel death was near.” Two neighbours, Ceri Williams and Peter Bielecki, testified that Bailey had told them he also assaulted his former wife, Sarah Limbrick. Judge Moran nonetheless fined two newspapers for failing to prove the allegation.

When Bielecki took Thomas to hospital in 1996, he testified: “Jules was curled up in almost the foetal position, at the foot of the bed, and was making these terrible animal-like noises. She had some hair in her hands … her eye was purple and there was blood coming out of it. Her face had gouges in it and she had teeth marks on her arm … It was the most appalling thing I’d ever witnessed.” All this the Bouniols learned from the libel trial. On the night Sophie Toscan du Plantier was murdered, Bailey left the house he shares with Thomas. He had scratches on his face the next day, and material was seen burning in his garden on St Stephen’s Day. He reported startlingly accurate details of her killing in the newspapers for which he freelanced, for example, in the Sunday Tribune dated December 29th, 1996: “The evidence indicates that she was pursued down the rocky track from her home and killed by repeated blows to the back of the head.”

Marie Farrell testified at the libel trial that she had seen Bailey at Kealfadda Bridge, about 1.5kms from Sophie’s house, on the night of the murder, and that he later sat in his car outside her shop in Schull, and made threatening gestures, drawing his finger across his throat, holding a finger against his temple. Farrell retracted her testimony in 2005 after repeated meetings with Bailey’s lawyer, as confirmed by him to The Irish Times at the time.

Marguerite Bouniol is absolutely convinced that Ian Bailey killed her daughter. The Supreme Court’s decision not to extradite Bailey to France last year was the worst blow since her daughter’s death, she says. She and Georges are mystified by what they perceive as the power of Bailey. They ask if he is being protected. “Bailey has run the show, from the beginning, when he talked to the foreign journalists who went to report on Sophie’s murder. He’s the one who started the story she had a lover in France.” In the Sunday Tribune, Bailey reported that “on several occasions [Sophie] had visited west Cork with different companions”. Georges finds the August 15th, 2008, letter from then director of public prosecutions James Hamilton in a file. “I made a decision not to institute any prosecution in respect of the murder,” Hamilton wrote. “You will appreciate that … it remains the policy of the Office not to give reasons for not prosecuting.”

Georges calls the DPP’s letter “a dismissal”. He repeats the word several times, incredulously: “It’s a dismissal … If it’s not Bailey, then why haven’t they found the killer?” This year, the French government recognised the Bouniols as victims of Sophie’s murder by awarding the family €115,000 in damages. “I didn’t even know the state could do that,” Marguerite says. “It helps pay our legal fees. At least France made a gesture. Ireland has never made a gesture.”

With the release of a report criticising the Garda Síochána’s handling of the case, Bailey has successfully shifted blame and suspicion from himself to the Garda. When Marguerite learned that Bailey and Thomas are suing the Irish State for wrongful arrest, “I thought, it serves the Irish State right,” she says bitterly. “Because they’re going to have to pay something.”

Their grandchildren have been the only consolation, the Bouniols say. Especially Baptiste, who was born three days before Sophie was murdered. For years, Georges took Baptiste to school, prepared his afternoon snack. Last year, Sophie’s son Pierre-Louis and his wife named their daughter Sophie. “It was hard for us,” Marguerite says. “I call her little Sophie.”

Sophie Bouniol was christened at Saint-Eustache church, near the Bouniol’s apartment, and confirmed at Notre Dame cathedral. I asked Marguerite if faith has been any comfort. “Religion helps those who truly believe,” she answered.

Marguerite told Fr Denis Cashman, the priest who performed the last rites over Sophie’s body, that she no longer believes in God.

“He said, ‘Do you believe in the devil? If there’s a devil then there’s a God too, and God doesn’t always win.’ That gave me a lot to think about.”

THE MURDER OF SOPHIE TOSCAN DU PLANTIER

December 23rd, 1996 The body of Sophie Toscan du Plantier (39) is found in the lane outside her holiday home near Schull, west Cork. Cause of death: laceration and swelling of the brain, fracture of the skull, multiple blunt head injuries

February 1997 and January 1998 Englishman Ian Bailey is arrested and questioned by gardaí. His partner Jules Thomas is arrested in 1997 and 2000. They are suing the State for wrongful arrest

January 2004 Judge Patrick Moran rules that eight newspapers were justified in identifying Bailey as the chief suspect in the death of Sophie Toscan du Plantier

2009 Toscan du Plantier’s family file a suit against Ireland for denial of justice with the European Court of Human Rights

March 2012 Supreme Court bars Bailey’s extradition to France. Bailey cannot leave Ireland because he risks arrest under the European arrest warrant issued by French Judge Patrick Gachon

May 2013 Bailey wins High Court order for the 20,000-document Garda file to be divulged to him

Autumn 2013 Judge Gachon to return to Ireland to interview some 30 witnesses

2014-2015 Judge Gachon is expected to complete his investigation and send the case to an assize court for a murder trial in absentia